This invention relates to an apparatus and method for determining the state of an automatic transfer switch. More specifically, the invention is directed to a method of, and the construction of apparatus for, determining the position or state of an automatic transfer switch from voltages readily available without need for special switch position contacts.
An electronic control circuit for an automatic transfer switches must monitor the position of the transfer switch in order to initiate proper action in response to a power outage or restoration. It is known in the art to provide an automatic transfer switch with auxiliary position contacts for determining the state or position of the switch. The control circuit is operatively connected to the position contacts for determining whether the contacts are open or closed. Because the auxiliary position contacts are mechanically linked to the main contacts, the state of the switch can be determined.
The use of auxiliary contacts is inefficient and expensive. The contacts themselves and their inclusion in the structure of an automatic transfer switch are costly. Moreover these contacts are subject to wear and breakage. In addition, special circuitry must be connected to the contacts to monitor their open/closed state.